This invention relates to a process for increasing the efficiency of a compression device and to a device for performing the process.
It is known how to alter the conveyed volume flow of helical compressors of the middle and upper power class by means of an axial power valve spool. The purpose of the power valve spool is to assist and to enable the start-up of the helical compressor during the start phase. During the start phase, the power valve spool is opened, and the compressor only conveys a reduced volume flow. After start-up, the power valve spool is closed; and, during the following operational phase, the volume flow is 100%. In the field of cryogenics, helical compressors are used for the compression of helium, for example. As published in the art "The Linde-Turborefrigerator for MR-Tomographs, J. Clausen et al., Advances in Cryogenic Engineering, Vol. 35, pp. 949-955, Ed. R. W. Fast, Plenum Press, New York, 1990", the control of the suction pressure is known by determining the suction pressure with a pressure measuring device and influencing the rate of mass flow by a bypass valve switched parallel to the helical compressor so that the suction pressure is maintained at constant values.
If this control concept is used in cryogenic installations for load cases which are hard to predetermine, such as, for example, in research centers in the cooling of superconductive magnets, then in partial load operation, which normally lies between 50% and 100% of the maximum conveying capacity, the result is a considerably reduced efficiency of the compression device.